Study On Shrinkage And Creep Effect For Long-Span Continuous Rigid Frame Bridge’s Long-Term Deflection

Continuous rigid frame bridge has become very popular due to the convenient construction method, large span length and comfortable travel. However, in recent years, many bridges have suffered from some damage problems, such as excessive mid-span deflections. One of the main reasons causing this problem is creep and shrinkage effects of concrete. At present, bar system FEM based on uniaxial experiment is mainly used in the calculation of creep and shrinkage effects. Therefore, it’s significant that how to analyze the spatial effect of concrete shrinkage and creep on long-span continuous rigid frame bridge’s long-term deflections by utilizing large software.In this thesis, the main research contents is as follows:(1) The development course of continuous rigid frame bridge, disease of down deflection and it’s research status, the factors that influence the creep and shrinkage effects were briefly introduced. The common concrete creep prediction models at home and abroad, creep computing theory and methodology were also compared and analyzed.(2) Combined with the condition that longitudinal cracking at box beam web plates of the main bridge of a super-long bridge, a continuous rigid frame bridge (118m+210m+118m) at Neijiang-Suining Express Way during the construction period,3D solid element model was established. The spatial effect of concrete shrinkage was simulated and calculated. The influence of spatial effect of concrete shrinkage for longitudinal cracking at Web of Segment No.1were explained.3D solid element model and bar system FEM were separately used for the analysis of main beam deformation, and their analysis results are contrasted. Finally some significant conclusions were reached.(3) With the application of the large nonlinear and detail analysis software MIDAS/FEA, the3D solid element model, which is of the main bridge of a super-long bridge, a continuous rigid frame bridge (95m+180m+95m) at Lijiang-Panzhihua Express Way, was established. The construction stages were simulated and the spatial effect of concrete shrinkage and creep were calculated. The stress and deformation condition at different constructing stages and the completed bridge after10years later were analyzed. Compared with the results of the space bar FEM model which was established by the finite software MIDAS CIVIL, some important conclusions were drawn.